1. Field of the Invention
The present invention relates to a tape cassette having a reel hub journaled on a reel shaft.
2. Background of the Prior Art
Tape cassettes containing separate supply and take-up reels that link a length of narrow magnetic recording tape are widely used. The known tape cassettes are generally classified into two groups according to the manner in which a reel hub is supported. The tape cassettes classified in a first group include a reel hub adapted to be supported on and driven by a shaft of an external drive unit. On the other hand, the tape cassettes of a second group have an internal or built-in reel shaft rotatably supporting thereon a reel hub. The second group of tape cassettes includes a take-up reel of VHS-C video tape cassettes ("VHS-C" is the trademark of Victor Co. of Japan, Ltd.).
A conventional take-up reel of the VHS-C type video tape cassettes generally includes, as shown in FIGS. 5 and 6 of the accompanying drawings, a reel hub 2 molded of a synthetic resin and having a generally cylindrical outer wall 2a for winding therearound a magnetic tape (not shown) and a cylindrical inner bearing wall 2b concentric with the outer wall 2a and having a central bearing hole 2c. The outer wall 2a is partly offset so as to form an arcuate clamp wall 2d defining an arcuate recess 2e for receiving therein a tape clamp (not shown) for fastening one end of the magnetic recording tape to the reel hub. The outer wall 2a and the clamp wall 2d are joined with the inner bearing wall 2b by a plurality of radial reinforcement ribs 2f.
The take-up reel hub 2 of the foregoing construction is rotatably supported on a reel shaft 3 which projects perpendicularly from the bottom wall of a molded cassette body 1 as shown in FIG. 7. The reel shaft 3 is made of metal and secured to the bottom wall of the molded cassette body 1 by means of a locking pin 4 press-fitted into an axial central hole 3a in the reel shaft 3 through a hole 1a in the bottom wall.
The tape-up reel hub supporting structure of the foregoing construction is composed of a relatively large number of component parts and hence the conventional VHS-C type video tape cassettes are costly to manufacture
To cope with this difficulty, the reel shaft 3 may be integrally molded with the bottom wall of the cassette body 1. In this instance however a satisfactory result cannot be obtained because an integrally molded reel shaft having the same diameter as the conventional one, such as 3 mm, is not resistant to a lateral force applied thereto in a direction perpendicular to the axis of the reel shaft. Accordingly, the reel shaft is likely to be damaged or broken when subjected to an impact or shock force imposed thereon for instance when the user unintentionally drops the tape cassette. In the case of an integrally molded reel shaft having a diameter greater than 3 mm, the bottom wall of the cassette body tends to have a sink mark in the vicinity of the reel shaft. With this sink mark the perpendicularity of the reel shaft is considerably deteriorated. Furthermore, the contact surface area between the reel shaft and the bearing hole of the reel hub increases with the diameter of the reel shaft with the result that the reel hub while being rotated is subjected to an increased friction resistance and hence tends to cause a running failure.